Feels like: You are aware of the blood flowing through the artery but no pressure is felt moving outward from the interior of the artery. No Qi is felt moving outward in the artery wall. A Thin pulse has the feeling that the wall wants to dilate but can’t because there’s not enough mediumship helping to generate a vibration.
A Thin pulse indicates a deficiency of mediumship. The medium that is deficient can be determined by the depth and the pulse position. For example, a Thin pulse in the moderate level of the Liver position indicates a deficiency of Blood. A Thin pulse in the deep level of the left Kidney pulse would indicate a deficiency of Jing. Classically, a Thin pulse does not describe the width felt. A Thin pulse is one in which you feel the artery not filling with mediumship sufficiently to create an outward pressure on the internal walls of the artery.